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This talk explores the role of grammatical tone in the verb system of Rere (Kordofanian, Sudan) based on primary data collection. Grammatical tone indicates Tense-aspect mood (TAM) in combination with a verbal suffix and auxiliaries. Verbal arguments are expressed by noun class agreement prefixes and pronominal enclitics. The position and segmental form of these markers does not change, but whether they expone subject or object depends on syntactic configuration. Subject topic sentences are SVO, class agreement is with the subject, and object pronominals appear post-verbally as enclitics: CL.SBJ-Verb=OBJ. However, Object topicalization (of a nominal or 3rd person pronominal) requires class agreement with the object and a post-verbal subject: OVS, or CL.OBJ-Verb=SBJ if the subject is pronominal. The verb forms are distinguished by tone on the enclitics. We argue that grammatical tone expones both case and number of pronominal enclitics. Furthermore, we show how the tone of pronominal enclitics is dominant with respect to TAM grammatical tone. It both overwrites it and blocks a high tone spreading rule that TAM tone does not block.